Camera focusing mechanism



y 1935- G. A; MITCHELL CAMERA FOCUSING MECHANISM Filed Feb. 23,. 1934 5 Sheets-Sheet l 33 Inventor George .19. mitt/a l l.

May 7, 1935. G. A. MITCHELL CAMERA FOCUSING MECHANISM Filed Feb. 25, 1934 I Inventor 4 Georgeffllmtshell.

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Patented May 7, 1935 Y UNITED STATES PATENT OFFICE; v

to Mitchell Camera Corporation, West Hollywood, QaliL, a corporation of Delaware Application February 23, 1934, Serial No. 712,545 27 Claims. (01. 95-45) This invention has general reference to lens- Fig. 2 is a side elevation of the camera shown changing and compensating focusing mechain Fi 1; nisms for motion picture cameras. Fig. 3 is a vertical longitudinal section taken a Motion picture cameras are ordinarily equipped on line 1-3 of Fig. 2;

with a plurality of photographic lenses of dif- Fig. 4 is a horizontal section taken as indi 5 fering focal lengths for use under varying circated by line 4-4 of Fig. 3; cumstances, and these lenses are sometimes car Fig. 5 is a vertical detail section taken on line ried on a rotatable lens turret mounted on the 5-5 of Fig.

head of the camera and operable to bring any Fig. 6 is a detail section taken on line 6-6 v selected lens into alinement. with the photoof Fig. 3; 10

graphicaperture, or there may be provided Fig. 7 is a vertical section 'taken on broken single lens holder permanently alined with the line of Figphotographic aperture and adapted to remov- 8 is a V w to n e a S taken ably receive the lens called for by the instant from Figoccasion. 'In either case, as is well known, the Fig. 9 is a section taken on line 9-4 of Fig. 8; 15 lens focusing mechanism or focusing scales must 0 s a eta l taken as di a ed by line be designed to compensate for the diflerent focal 0 01 Fi d f length lenses used in the camera, since the dis- 11 s detail of e 110117101191 the a Of tance a given lens must be moved in focusing is the a a.

a0 determined by the focal length of that lens. For p i y f illustration the camera box Means have accordingly been provided in the d magazine mounted thereon i only convenprior art for adjusting the velocity ratio between tiohally illustrated, Since t'heSe Parts d e the manual focusing member and the movable mechanism wi hin may be of any suitable 0r lens'mount for the purpose 'of compensating these 11511911 yp e invention in s P e t f differences, so that by properly adjusting the is Particularly adaptable to the Mitchell ype of 25 focusing mechanism each time a lens change is camera, which comprises base, a s ret eifected, a fixed range of movement of the manual carrying head rising'from the forward d therefocusing member along a fixed distance scale is of, n a camera box Slidfible v e yen the made to serve for 311 1en5e5 base directly behind the head, and the inven- It is one object of the present invention to protion is here illustrated in connection with this 30 vide an improved focusing mechanism of the type of C It is to be understood, w-

type having compensating adjustment means for ever, typifiCatiOn 0f the invention varying its velocity ratio to correspond with the merely illustrative of rather h nmitative on various focal lengths of lenses to be used. the ihvehtihh- Broadly, it is immaterial to this aspect of'the in- In the drawings humeral designates 35 vention whether the camera is of the lens turret erahy Such a Picture camera comprising type carrying a plurality of lenses or of the inbase I], head rising from the forward end of gle lens holder type as t present f u ing said base, camera box l3 supported on base H mechanism is adaptable to either situation. immediately to the rear head d slidable 40 It is another important object of the inventransversely 011 the base in ways I4, and film 0 tion, however, -to provide automatic means for magazme mounted on camera box within accomplishing the focusing mechanismcompen- P the usual ixposure aperture plate and sating adjusting each time a difierent lens is mtemuptent mechan-lsmfor moving the film F placed beiomihe photographic aperture In past said plate, these parts not being illustrated this aspect the lens turret form ofc'amera is Since mesh be of 1". conventional design 45 Primarily, though perhaps not essentially; in view. gwhen T camera box positioned at the right The invention itself will best be understood 333 zgi g ifig gfig g f t g gggg g from the following detailed. description of a. almement with the photographic aperture A of present illustrative embodiment thereof, referthe camera head and is therefore in 50 once for this purpose being had to the accomposition.

ma' er m h When the photographic lens is to be accurately u e 1 S a Side l v on' Of a conventional focused camera box I3 is moved transversely to motion picture camera equipped with my inventhe left and an optical focusing tube, not shown, 1; l is brought into .alinement withaperture A and 55 the photographic lens then in position before the aperture. After focusing, the camera box is returned to the photographing position of Fig. 2.

The camera base includes an upper horizontal base plate 20 which supports camera box l3, and vertical sides 2| and 22 integral with and depending from plate 20. A bottom wall 23 is fastened between the lower edges of side plates 2| and 22. At the forward end of base plate 20 is a vertical head plate 25,'said head plate being immediately forward of the transversely movable camera box. Mounted adjacent the forward side of this plate 25 is turret-carrying head casting 27. This casting is formed with a forwardly extending annular flange 28, within which is rotatably taken a turret carrying ring 29. A retaining ring 30 affixed to the outer end of flange 28 overhangs said ring 29 and confines it within flange 28. The photographic lens turret 32, provided as shown with spaced photographic lens mountings 33, 34, 35 and 36, is mounted within ring 29, and is non-rotatable with reference to saidring but is limitedly extensible forwardly from the ring from the retracted full line position illustrated in Fig. 3. Although various mountings to accomplish this 'purpose may be utilized, I show a preferred mounting comprising a set of four bearings, each embodying a bearing ball 3| retained between longitudinal V-shaped grooves 3la formed in bearing members 3'! and 38 set into slots cut in the inner surface of ring 29 and the periphery of turret head 32, respectively. Members 3! project as shown forwardly from ring 29 in orderto accommodate the required forward extension of the turret. Retaining means, as pins (Mb, 310 and 3ld may be provided to prevent loss of the balls. It will be evident that the turret is free 'to move on its axis in and out of ring 29. It will also be evident that the balls retained in the V-grooves of members 31 and 38 key turret 32 against relative rotation within ring 29.

, alinement with the photographic camera aperture A, I show the head flange 28 provided'at the top with a spring pressed locking plunger H0 adapted to be projected by a spring I I l into prop erly located apertures H2 in the periphery of turret carrying ring 29. The upper end of said Plunger has afinger piece H3 by means of which it may be conveniently manipulated.

The lens turret has been described as freely movable forwardly and rearwardly with reference to the camera body, and in accordance with the here illustrated form of the invention this bodily movement of the turret is utilized in focusing the photographic lenses, which are mounted in fixed position on the turret. The lens focusing mechanism is therefore connected directly to turret 32 for the purpose of moving it and the lenses carried thereby bodily forwardly or rearwardly in making focusing adjustments:

In the present form of the invention, turret 32 has a hub 40 and a central axial bore 4|, and is rotatable on a tube 42 within bore 4|. Tube 42 has near its rearward end an annular flange 43 which is confined within an inwardly facing annular groove 43a afforded by flanged ring "44 mounted in turret countersink Ma. The turret is free to rotate on tube ,42, but is prevented by flange 43 and ring 44 from axial movement relative thereto.

Extending axially through the bore of tube 42 and through a bore 45 in wall 25 is a mounting pin 46 having an enlarged head 46a received within a countersink 46b in therear surface of head plate 25. This pin may be fastened in place as by screws 46c.

A shaft 41 extends axially through pin 46 and is arranged to move freely longitudinally of the pin but is non-rotatable with reference thereto. As-shown, shaft 41 and the opening through pin 45 may for this purpose be square in cross section. The forward end of shaft 41 has an enlarged flat head 41a which is of the same diameter as turret boss 40 and faces against the outer end thereof, as shown, and is afflxed as by screws '4'") to the end of tube 42 on which the turret is rotatably mounted. Tube 42, being fast to nonrotatable but longitudinally movable shaft 41, is thus fixed against rotation, but is arranged to move and to carry the turret in a direction longitudinally of its axis. Between pin 46 and tube 42 is a gear sleeve 48 having at its opposite ends conical seating surfaces 49 bearing against balls 50 confined between pin shoulder 5! and washer 52, the latter mounted on the forward end of pin '48 and being set up by means of a nut 53 on the screwthreaded forward extremity of said pin.

A screw connection is provided between gear sleeve 48 and tube 42. Instead of utilizing conventionalscrewthreads for this purpose, however. I preferably provide a freely operable anti-friction screw connection between these members. For this purpose the exterior surface of sleeve 48 and the interior surface of tube 42 are cut with corresponding spiral, V-shaped grooves 56 and 51, respectively, and placed in the spiral raceways thus afforded are bearing balls 58. In order to give the screw a comparatively long lead, double spiral grooves may preferably be provided, as indicated. A ball cage 54 is preferably provided, and serves 'to space the balls along the spiral raceway. There is thus provided an anti-friction screw connection between sleeve 48 and tube 42, and it will be evident that upon rotation of sleeve 48, tube 42 and the lens turret mounted thereon are screwed forwardly and rearwardly with reference to turret mounting ring 29.

For the purpose of so rotating sleeve 48, said sleeve has near its rearward end spur gear teeth 68 in mesh with rackgear teeth 6| of a member 52 lying between turret head 32 and wall 25 and accommodated within a recess 21a formed in head casing 21 for horizontal movement transversely of the camera (see Fig. 7). Said member 62 has near its lower edge a horizontally extending dovetailed portion 63 which slides within a dovetailed way 64 cut in wall 25, as shown clearly in Figs. 3 and 4.

Member 62, which may be referred to as a. slide member,'is moved back and forth by a lever 10 which extends rearwardly through camera base I l, and'which has a forwardly and rearwardly adjustable vertical fulcrum axis 3-3. This 1cver transmits motion to rack gear 6| from a rearward slide member 19, which is constrained to .-movement parallel to the movement of slide memshow it'as 'a telescoping forward sleeve H and rearward rod 12, the sleeve having fastened therein, as by pin'13, a forwardly extending rod 14. The forward and rearward extremities of the leand the pivot pin 15 isset into the dovetail, as.

clearly shownin Figs. 3 and 4.

Slide member 18 has afilxed thereto a rack gear 82 meshing with a gear 83 which is mounted on a shaft 84, said shaft being joumalled in the rear wall of a housing member 86 that closes the rear side of the camera base. On the rear end of shaft 84 is a manual operating arm or crank 81.

The adjustablepivot mounting for the lever comprises a sleeve 98 within which lever sleeve 1| is longitudinally slidable, and which sleeve 88 is vertically trunnioned on axis 3-3 in slide carriage 8 l Thus sleeve 98 is furnished with upper and lower trunnions 83 and 94 which are respectively .rotatable in carriage slide plate 85 and yoke 85 suspended from said plate 95, in the manner clearly shown in Fig. 6. The arms of the yoke 96 are laterally spaced on opposite sides of sleeve 85 to give the necessary clearance for the required angular swing of said sleeve with the lever. Plate 95 is of dovetailed cross section and slides longi-- tudinally of the camera, and of lever 10, in a dovetailed way 91 cut in a guide plate 58 secured to the underside of base plate 28. The means for moving the fulcrum slide carriage with reference to guide plate 98 will be described hereinafter, it being sufficient for thepresent to note that sleeve 98- and its fulcrum mounting are shiftable by.

movement of carrier plate 95 in guide plate 88.

From the foregoing it will be evident that operation of manual control arm 81 acts through gears 83 and 82 and slide member 18 to swing lever 18 on fulcrum axis B-B, causing translation of rack 6| and rotation of gear 68 and sleeve 48 to produce forward or rearward movement of the lens turret. In this action lever sleeve 1| and lever rod 12 have telescopic movement with reference to each other, and sleeve 1| has of course some sliding movement within trunnion sleeve 40. Thus it will be evident that the two pivotconnections 15 and 18 at the ends of the variable length lever 18 move in lines which are parallel to each other. From this it will be seen that the amount of movement of pivot 15 and hence of slide member 62 will always be in direct proportion to the amount'of movement of slide member 19 and its pivot connection 18 with the lever. The amount of such movement imparted to slide member 62 by a-given movement of slide member 19,-however, obviously depends upon the position of the lever fulcrum along the length of the lever, and such an adjustment is utilized to vary thevelocity ratio of the mechanism to suit various focal length lenses. 1 have provided automatic means for accomplishing this adjustment in accordance with rotation of the lens turret in bringing various focal length lenses before the photographic aper: ture A of the camera although this provision will not be used in cases-wherein the len's turret or some similar movablelens carrier is not utilized,

as for instance where the camera is furnished with but asingle lens holder. Forthls reason the mechanism will first be considered without regardto the automatic fulcrum adjusting means,

and for this purpose it is assumed that the ful crum carriage is to be moved in its guide manually. It will be obvious that suitable scales, calibrated in focal lengths of lenses, may be pro- Now there is obviously one position for the lever which is common for all positions of the fulcrum along its line of movement, i. e., parallel to the direction line of fulcrum adjustment movement, or,

in the present specific case, perpendicular to the lines of movement of slide members 62 and 18. This common lever position, which is shown in full lines in Fig. 4, is made the position for infinity focus, and at this common infinity position the rearward slide member 19 and manual operating member 81, and also the forward slide member 62'and turret driving gear sleeve 48 operated-by the-lever, as well as the turret itself, obviously take a common position for all positions of adjustment of the lever fulcrum. Adjustment of the position of the lever fulcrum when the lever is in this described infinity position (parallel'to the direction line of fulcrum adjustment) thus serves simply to move fulcrum sleeve 90 longitudinally on lever sleeve 1|, without affecting the position of the lever, and consequently without altering the position of members 62, 48, and the lens turret.

The lens turret is thus seen to have 'a fixed, definite position along its axis for the described infinity position of the lever. The photographic objectives are then so mounted on the turret that when the turret is in this fixed position for infinity focus, each objective is located ahead of the focal plane of the camera (the film) by a distance equal to its own focal length.

Assuming the parts their .to be in the full line, infinity focus position represented in Figs. 3 and 4, movement of manual member 81' in a lefthanded direction, as viewed from the rear of the treme forward or close-up focusing position indicated in dotted lines in Fig. 3. And the amount of this forward-movement imparted to the lens turret by a given movement of manual member 81 depends of course upon the adjusted location of the lever fulcrum, as previously explained.

Thus by longitudinal adjustment of the fulcrum position of the lever member, the velocity ratio between manual focusing member 81 and lens turret 32 is varied, and if a fixed distance scaleis provided for the manual member, (or for any invariably moving part of the mechanism between the manual member and the lever), starting with the common position for all lenses for infinity focus and marked off at suitable distance intervals on down to close-up, then proper positioning of the fulcrum so adjusts the mechanism that full movementof manual focusing member 81 over thisfixed range of positions from infinity to close-up produces any total range of lens turret movement requiredfor any focal length lens.

For instance, I have here shown the rack gear 82 on rearward slider member 18 provided with an indicator 88 which extends rearwardly through for accomplishing the fulcrum adjustment auto matically by virtue of rotation of the lens turret in bringing difierent lenses into alinement with the photographic camera aperture A. Fbr this purpose, in the present embodiment, the turret carrying ring 29 is furnished with bevel gear teeth I which mesh with a bevel gear I M journalled at I02 on the camera base bottom 23. The ratio of gear ring 29 to gear IOI is preferably one to one, so'that gear IOI makes one complete revolution for one complete revolution of the lens turret. The center of gear IN is preferably, directly under lever I0 when'said lever is in itsfright angle or infinity focus position (Fig.

Q. The upper face of bevel gear IOI carries a cam member I03 having a continuous, upwardlyfacing cam groove I03a, this cam member and groove preferably extending entirely around the center of gear MI and closing on itself, as shown. It will be noted from Fig. 4 that lever 10, along which the trunnion carriage 96 is slidable, twice intersects cam groove I03a; the lower sleeve trunnion 94 is then provided with a follower bushing I05 which engages in the cam groove I03a at the forward intersection of said groove by lever I0, or in other words, between the center of gear IN V and slide member 62. Rotation of the lens turret to bring different focal length lenses into photographing position acts through balls 35 to rotate bevel gear ring 29, thereby causing rotation of bevel gear I 0| meshing therewith, and this rotation causes cam groove I03 to act on the cam follower extremity I 04 cf the lower lever trunnion to move said trunnion along itsfixed line movement, thereby adjusting the trunnion axis of lever I0 to correspond-with the focal length of the lens which is being moved into position. The cam groove I031; is accordingly so designed that when the turret is rotated to bring any one of the lenses to photographing position, the cam groove has moved the trunnion carriage to such position as will give the proper velocity ratio between-the two ends of lever member I0 for that lens.

Assuming now four photographic lenses equally I spaced about the lens turret and having differing focal lengths, the cam groove is provided with four points or positions, spaced 90 apart, which come successively into engagement with the lower pivot end of the trunnion carriage to adjust the position of the trunnion axis along lever I0,.and these points are of course so located on gear IOI as to bring the fulcrum axis to the properpositions along'the length of the lever for the corresponding lenses on the turret. As here shown, these points are included within 20 circumferential sections a, b; c and d of the groove, and by this provision the fulcrum axis is in adiusted position within of are on either 'side of the final position of cam gear I, thus providing a margin of safety to care for any back lash in-the mechanism, and fully assuring that when p the turret has moved a lens to photographing position, the fulcrum will be accurately in position to give the mechanism that required velocity ratio for that lens.

-20 circumferential cam groove sections a, b, c and d are connected by smooth curved a slot 89 in the rear wall of housing member 86,

connecting portions, as shown, so that the trunnion carriage will move easily as the lens turret and gear I0l are rotated. Preferably, the 20 cam sections for the longest and the shortest focal length lenses are placed opposite one another on gear IOI this being of advantage in that the long and short focal length lenses are then opposite one another on the lens turret, so that the long lens tube of the former will not interfere with the wide angle field of the latter. Fig. 4 accordingly shows the short focal length cam section 0 directly across from the longest focal 'cam section 0. It will be noted that with the continuous type of cam here provided, the turret may be rotated in either direction to bring a desired lens into photographing position and to set the velocity ratio of the focusing mechanism.

It is of course possible to utilize more or less than four lenses on the turret, as space will permit, and it is not necessarily essential that the lenses be uniformly spaced about the turret, the shape of the cam groove in any case being simply designed to bring the lever fulcrum into proper position for the lens at that time alined before the aperture. It is to be understood that the drawings and description are to be considered merely as illustrative of and not restrictive on the broader claims appended hereto, for various changes in design, structure and arrangement may be made without departing from the spirit and scope of said claims.

I claim:

1. In a lens focusing mechanism, the combination of a movable lens carriermember adapted to be moved to carry a lens forwardly and rear wardly, and means for moving said carrier member embodying a lens carrier operating member movable in a straight line and operably connected with said lens carrier member, an operating lever connected to said member, and a fulcrum for said lever adjustable in a direction at right angles to the line of movement of said lens carrier operating member.

2. In a lens focusing mechanism, the combination of a movable lens carrier member adapted "to be moved to carry-a lens forwardly and rearwardly, and means for moving said carrier member embodying an operating lever operatively interconnected with said'len's carrier member and adapted to takea position wherein said lens carrier is in a rearward infinity focus lens position, and'a fulcrum for said lever adjustable in a' direction line parallel to said lever position for infinity focus.

3. In a lens focusing mechanism, the combination of a movable lens carrier member adapted to be moved to carry a lens forwardly and rear-,

wardly, and means for moving said carrier member embodying a slide member movable in, a straight line, another slide member movable in a line parallel to said first slide member, a lever for transmitting motion between said slide members, and fulcrum for said lever adjustable along a straight line to different positions relative to said slide members.

4. In a lens focusing mechanism, the combinaand a fulcrum for said lever adjustable along a.

straight line to different positions between said slide members.

6. In a lens focusing mechanism, the combination of a movable lens carrier member adapted to be moved to carry a lens forwardly and rearwardly, and means for moving said carrier mem-- ber embodying a slide member movable in a straight line, another slide member movable in a line parallel to said first slide member, a lever connected at itstwo ends to said slide members, and a fulcrum for said lever' adjustable along a line at right angles to said slide members.

Cal

7. In a lens focusing mechanism, the combination of a movable lens carrier member adapted to be moved tocarry a lens forwardly and rearwardly, and means for moving said carrier member embodying a slide member movable in a straight line, another slide member movable in a line parallel to said first slide member,a lever for transmitting motion between said slide member and adapted to take a'position wherein said lens carrier is in a rearward infinity focus lens position, and a fulcrum for said lever adjustable in a direction line parallel to said lever positionfor infinity focus.

8. In a lens focusing mechanism, the combination of a movable lenscarrier member adapted to be moved to .carry a lens forwardly and rearwardly, and means for moving said carrier member embodying a slide member movable in astraightline, another slide member movable in a line parallel to said first slide member, an extensible lever pivotally connected at one end with one of said slide members and pivotally connected at the other end with the other of said slide members, and a fulcrum for said lever adjustable to diiferent positions between said slide members.

-9. In a lens focusing mechanism, the combination of a movable lens carrier member adapted to be moved to carry a lens forwardly and rearwardly, and means for moving said carrier member embodying a slide member mdvable in a straight line, another slide member movable in-a line parallel to said first slide member, an extensible lever embodying two telescoping sections, a pivot connection for one of said sections to one of said slide members and a pivot connection for the other of said sections with the other of said slide members, and a fulcrum for said lever adjustable to different positionswith reference to the lever. 10. In a lens focusinglmechanism, the combination of a movable lens carrier member adapted to be moved to carry a lens forwardly and rearwardly, and means for moving saidcarrier mem-r ber embodying a slide member movable in a straight line, another slide member movable in a line parallel to said first slide member, an extensible lever embodying two telescoping sections, a pivot connection for one of said sections with one of said slide members and a pivot connection for the other of said section's with the other of said slide members, and a fulcrum for said lever adjustable along a line at right angles to the directions of movement of said slide members.

11. In a'lens focusing mechanism, the combi-; nation of a movable lens carrier member adapted to be moved to carry a lens forwardly and rear wardly, and means for moving said carrier member embodying a slide member movable in a straight line, another slide member movable in'a line parallel to said first slide member, an extens'ible lever embodying telescopically arranged tube and rod sections, a pivot connection between said rod section and one of said slidemembers, a pivot connection between said tube section and the other of said slide members, a sleeve slidably taking said telescopic lever,. trunnion mounting means for said sleeve, and means for adjusting the position of said trunnion mounting means along said lever.

12. The combination comprising an-inner cylindrical member, mounting means supporting said member for rotation on its axis but holding it against movement along its axis, means for rotating said cylindrical member,--an outer tubular member surrounding said cylindrical member, the

- outer and inner surfaces of said inner cylindrical and outer tubular members respectively having spiral grooves formed therein, balls in the spiral raceways afforded by said grooves to interconnect said members, and supporting means guiding said outer tubular member to move along its axis but restraining said member against. rotation on its holding said tubularmember against rotation.

on its axis, a lens turretrotatably mounted .on

but restrainedagainst axial movement with reftudinal movement along its axis, means for rotating said cylindrical member, an outer tubular member surrounding said cylindricalmember, the outer and inner surfaces of said inner cylindrical member and said outer tubular member respec-- tively having spiral grooves formed therein, balls in the spiral raceways aiforded byv said grooves interconnecting said members, means holding said tubular member against rotation on its axis, a lens turret rota-tably-mounted on but restrained against axial movement with reference to said tubular member, a rotatable supporting member v for saidlens turret, means .in association with said supporting member guiding said turret to move along its axis but holding it-against rotation with reference to said member, and means for releasably holding the turret supporting member against rotation. I

15. In alens focusing mechanism, the combination comprising an inner cylindrical member, mounting means supporting said member -for ro- .against axial movement with reference to said tubular member, supporting means guiding said lens turret to move along its axis with longitudinal axial movement of said tubular member, and means for releasably holding said lens turret against rotation, on its axis; A

16. In a lens focusing mechanism, the combination comprising. an inner cylindrical member, mounting means supporting said member for rotation. on its axis but holding it against longitudinal movement along its axis, means for rotating said cylindrical member, an outer tubular member surrounding said cylindrical member, said outer tubular member havinga screw connection with said inner cylindrical member, a. lens turret rotatably mounted on but restrained against axial movement with reference to said tubular member, a rotatable supporting member for said lens turret, means in association with said supporting member guiding said turret to move along its axis but holding it against rotation with reference to said member, and means for releasably holding the turret supportingmember against rotation. I

l'ZTIn a lens focusing mechanism, the combination of a lens carrier member adapted to support a plurality of lenses, said member being mounted to move in a forwardly and rearwardly direction for focusing purposes and to be shifted in a direction transverse of said first mentioned direction to place different lenses in a given operative position, means including a manual operating member for moving said carrier member forwardly andrearwardly, said means embodying velocity ratio adjustment means whereby the amountof such movement imparted to the lens carrier by plurality of lenses, said member being mounted to move to place diiferentlenses in a givenope'rative position, means including a manual operatin member for effecting forward and rearward lens focusing movement, said means embodying velocity ratio adjustmentqneans whereby the amount of lens focusing movement imparted by a given movement of the manual member may be varied to suit different focal length lenses,

and automatic means for adjusting the last'mentioned means actuated by virtue of shiftingthe carrier member in placing ent lenses in said operative position. I

19. In a lens focusing mech the combi@ nation of a rotatable lens turret adapted to support a/plurality of lenses to be rotated'to place its lenses successively in operative position, said lens turret being mounted to move along its axis for focusing movement, means including a manual operating'member for eifectlng movement of the lens turret along its axis, said means embodying velocity ratio adjustment whereby the amount of lens focusing movement imparted by a given movement of the manual member may be varied to suit different focal length lenses, and

means for adjusting the last mentioned means actuated by virtue of rotation of the lens turret in carrying different lenses to operative position.

20. In a lens focusing mechanism, the combination of a rotatable lens turret adapted to support a plurality of lenses and to be rotated to carryits lenses successively to a given operative position, means including a manualoperating member for effecting focusing movement of said turret carried lenses, said means embodying velocity ratio adjustment means whereby the amount of lens focusing movement imparted by a given movement of the manual member may be varied to suit different focal length lenses, and means for adjusting the last mentioned means actuated by virtue of rotation of the lens turret in carrying lenses to operative position.

21. In a lens focusing mechanism, the combination of a rotatable lens turret adapted to support a. plurality of lenses, a turret carrying member rotatable on the axis of said turret, said ber for efiecting axial movement of the lens turret, said means embodying velocity ratio adjustment means whereby the amount of lens focusing movement imparted by agiven move- -ment of the manual member may be varied to suit different focal length lenses, and means actuated by rotation of said turret carrying member for operating said velocity ratio adjustment 22. In a lens focusing mechanism, the combination of a rotatable lens turret adapted to support a plurality of lenses: a turret carrying mem-' ber rotatable on the axis of said turret, said member supporting the turret for lens movement along its axis but holding it against rotation with reference to said member, said turret carryingmember adapted to be rotated to place different turret carried lenses in a'given operative'positlon, means including a manual operating member for effecting axial movement of the lens turret, said means embodying velocity ratio adjustment means whereby the amount of lens focusing movementimparted by a given movement of the manual member maybe varied to suit different focal length lenses, and gear means driven by rotation of the turret carrying member adapted to operate said velocity ratio adjustment means. 23. In a lens focusing mechanism, the combination of a rotatable lens turret adapted to support a plurality of lenses, a turret carrying mem ber rotatable on the axis of said turret, said member supporting the turret for lens movement along its axis but holding it against rotation with reference to said member, said turret carrying member adapted to be rotated to place different turret lenses in a given operative position, means for effecting axial movement of the lens turret, said means including a lever, and a fulcrum for said lever adjustable to different positions to vary the velocity ratio of said means, and means actuated by rotation of said turret carrying member for adjusting the position of said lever fulcrum.

,24. In a lens focusing mechanism, the combination of a rotatable lens turret adapted to support a plurality of lenses, a turret carrying member rotatable on the axis or said turret, said member supporting the turret for lens movement along its axis but holding it against rotation with reference to said member, said turret carrying member adapted to be rotated to place different turret carried lenses in a given operative position, means for effecting axial movement of the lens turret, said means including a lever, and a fulcrum for said lever adjustable to different positions to vary the velocity ratio of said means, a gear on said turret carrying member, a second gear meshing therewith, and means operated by the last mentioned gear for adjusting the position of the lever fulcrum to correspond properly with the focal length of lenses brought to operative position by rotation of the turret carrying member.

25. Ina lens focusing mechanism, the combination of a rotatable lens turret adapted to support a plurality of lenses, a turret carrying member rotatable on the axis of said turret, said member supporting the turret for lens movement along its axis but holding it against rotation with reference to said member, said turret carrying member adapted to be rotated to place difierent turret carried lenses in a given operative position, means for effecting axial movement of the lens turret, said means including a lever, and a fulcrum for said lever adjustable to different positions to vary the velocity ratio of said means, and cam means operated by rotation of said turret carrying member and adapted to adjust the position of the lever fulcrum to correspond properly with the focal lengths of lenses brought to operative position by rotation of the turret carrying member.

26. In a lens focusing mechanism, the combination of a rotatable lens turret adapted to support-a plurality of lenses, a turret carrying member rotatable on the axis of said turret, said member supporting the turret for lens movement along its axis but holding it against rotation with reference to said member, said turret carrying member adapted to be rotated to place diiferent turret carried lenses in a given operative position, means for effecting axial movement of the lens turret, said means including a lever, and an adjustable fulcrum for said lever constrained to move in a line along the lever to vary the velocity ratio of said means, a gear on said turret carrying member, a second gear meshing therewith, and a cam on the second mentioned gear adapted to move said fulcrum along its line of movement.

27. In a lens focusing mechanism, the combination of a rotatable lens turret adapted to support a plurality of lenses, a turret carrying member rotatable on the axis of said turret, said member supporting the turret for lens movement along its axis but holding it against rotation with reference to said member, said turret carrying member adapted to be rotated to place different turret carried lenses in a given operative position, means for effecting axial movement of the lens turret said means including a lever, and

'an adjustable fulcrum for said lever constrained to move in a line along the lever to vary the velocity ratio of said means, and cam means operated'by rotation of theturret carrier member adapted to move said fulcrum along its line of movement.

GEORGE A.- MITCHELL. 

